/**
 * Read-only view of the target pi-browser-harness persists for `/browser-target`.
 *
 * The stored value is the raw string a user would have put in BU_CDP_HTTP
 * ("local", "10.88.0.25:9223", …) — kept in that vocabulary deliberately, so
 * there is one resolution path in endpoint.ts and a stored value can never mean
 * something the variable could not.
 *
 * Every read failure degrades to "nothing stored" rather than throwing: a
 * corrupt or absent file must fall back to the built-in default, not break search.
 */

import { readFile } from "node:fs/promises";
import { targetFilePath } from "./paths.ts";

const CURRENT_VERSION = 1;

/**
 * The persisted target, or null when nothing is stored, the file is missing, or
 * it cannot be parsed. A file written by a newer version is treated as "nothing
 * stored" rather than guessed at.
 */
export const readStoredTarget = async (): Promise<string | null> => {
  let raw: string;
  try {
    raw = await readFile(targetFilePath(), "utf8");
  } catch {
    return null;
  }
  try {
    const parsed: unknown = JSON.parse(raw);
    if (typeof parsed !== "object" || parsed === null) return null;
    const file = parsed as Record<string, unknown>;
    if (file["version"] !== CURRENT_VERSION) return null;
    const target = file["target"];
    if (typeof target !== "string") return null;
    const trimmed = target.trim();
    return trimmed.length > 0 ? trimmed : null;
  } catch {
    return null;
  }
};